Chemistry is useful to human beings?
Chemistry is useful for human beings.
Combustion reactions are some of the most practically useful in chemistry. These reactions are also likely the first to be mastered by human beings (e.g. fire-making). Combustion reactions can be used to produce heat (such as for warming a dwelling or to cook food) and generate useful work (such as running a motor for an automobile). Combustion reactions can also be used to generate chemical compounds, such as carbon dioxide and water.
Most farm animals are useful for meat, chickens and cows produce eggs and milk. Other wild animals like monkeys, tigers and elephants can be ut into zoos to earn money. If you think carefully about it so many animals are useful to human beings and have been used for long time by early humans and still now.